Shock absorber with vacuum compensator



W. T. BLAKE SHOCK ABSORBER WITH VACUUM COMPENSATOR July 12, 1960 3 Sheets-Sheet 1 Filed July 30, 1956 INVENTOR William T.Bl0ke y BY ATTORNEYS July 12; 1960 w. 'r. BLAKE SHOCK ABSORBER WITH VACUUM COMPENSATOR S-Sheets-Sheet 2 Filed July 30, 1956 mvsmon William T. Bloke w w BY ATTORNEYS July 12, 1960 w. T. BLAKE snocx ABSORBER WITH VACUUM COMFENSATOR 3 Sheets-Sheet 3 Filed July so, 1356 WEiEEK EEZM R O T. N w mm M B G 4 m w Y B m 5 w R w a Mm, N\\/ /l ll mh a ATTORNEYS direction.

United States Patent I SHOCK ABSORBER WITH VACUUM COMPENSATOR William T. Blake, 4424 Morris Court, Fort Worth, Tex. Filed July 30, 19 56, Ser. No. 600,977 17 Claims. (Cl. 188-97) This invention relates tonew and useful improvements in hydraulic mechanisms and more particularly to shockresisting hydraulic mechanisms. p Y i r This application is a continuation-in-part of my copending application Serial No. 479,546, filed January 3, 1955, for Hydraulic Mechanism, now abandoned.

It is well known that railway cars, particularly freight cars, are subjected to many impacts or shocks of relatively great magnitude and that such impacts or shocks are amplified or multiplied by the number of cars in a given train. This is due in part to the fact that there is a certain amount of slack between the couplers of the cars. The cars tend to .bunc or crowd together on slowing or stopping of the prime mover or engine, on down grades and on entering curves, whereby each car bumps the car forwardly thereof and the combined impact of all of said cars is transmittedto the slower traveling foremost car. Oninitial movement or acceleration of the engine, on up grades and on leaving curves, the

cars tend to stretch or move away from one another so as to be jerked by the faster traveling cars thereahead and the combined stress or relative movement of all. of

the cars is exerted upon the rearmost car. Manifestly, these impacts or shocks damage the cars and particularly their contents as well as wear the couplers to thereby produce greater impacts or shocks in the future. Also, other equipment and machinery are subjected to similar shocks due to sudden stops, impacts, or changes in the direction of movement.

Moreover, when freight trains are made up severe impact stresses are set up in the couplers and draft gear and great shocks are imparted to the contents of the cars when cars are moved into impact with each other in effecting coupling. ,7

Accordingly, one object of the invention is to provide an improved hydraulic mechanism of such construction as to be particularly adapted for use in appreciably reducing the impacts or shocks exerted on machinery and equipment and particularly on railway cars and their contents through their couplings and draft gear upon relative movement of the cars. I

Another object of the invention is to provide an improved shock-resisting hydraulic mechanism for machinery and equipment, such as a railway car draft gear, which is arranged to permit limited movement of the coupler relative to its car While controlling the speed of such movement so as to cushion any shock or impact caused by the initiation or cessation of said movement.

A particular object 'of the invention is to provide an improved hydraulic mechanism, of the character described, wherein movement in either direction is controlled and wherein movement in one direction maybe ata different rate of travel than movement in the opposite I I compensating means to accommodate variations in the to provide an 7 a we volume of its interior whereby the unit may be completely filled with a non-compressible fluid.

A further object of the invention is to provide an improved'hydraulic mechanism, of the character described, which includes a hermetically-sealed housing having a cylinder mounted in and communicating with the interior of the housing and pressure-responsive, substantially tem-- perature insensitive, vacuum-filled means in the housing for permitting variation of the volume of its interior and the filling thereof with a non-compressible fluid.

Still another object of the invention is to provide an improved hydraulic mechanism, of the character described, having a piston reciprocally mounted in its cy1-. inder and of substantially the same length as its stroke, whereby the rate oftravel of the instroke and outstroke' of the-piston may be independently varied.

Another object of the invention is to provide an im proved hydraulic mechanism, of the character described, wherein the cylinder has inwardly opening check valves so that the rate of travel of the piston or force required to move the piston on its instroke and outstroke is primarily controlled by openings in the side wall of the cylinder.

Yet another'object is to provide an improved hydraulici mechanism, of the character described, having one or more adjustable valves for compensating piston movement due to unavoidable tolerance variations in the fit of the piston inthe cylinder occurring in manufacture or as a result of wear. 7

Still another object is to provide an improved hydraulic mechanism of the character described, having means for taining a vacuum with a spring mounted in the bellows or biasing the bellows to balance thebellows in expanded positions against the collapsing force of varying fluid pressure. p I

A further object of the invention is to provide a substantially temperature insensitive device for compensating changes in volume of a confined body of non-compressible or hydraulic fluid.

In summary, the foregoing and other aims, objects and advantages of the invention are achieved in a shockresisting hydraulic mechanism having a housing and a Working cylinder having end and side Walls mounted in the housing providing a chamber between the cylinder and the housing. In one form, the walls of the cylinder are spaced from the walls of the housing to provide a chamber, in effect, completely surrounding the cylinder.

A wall of the cylinder has an opening or openings establishing communication between the cylinder and the chamber and a piston is mounted in the'cylinder for reciprocation between its end Walls. The piston has a piston rod extending to the exterior of the mechanism through one of the end walls of the cylinder and sealingly through a wall 'of the housing. The chamber and cylinder are completely filled with a non-compressible fluid such as oil. A substantially temperature-insensitive compensating device is exposed to the fluid in the chamber for the purpose of compensatingfor fluid pressure changes;

in the chamber due to'temperature changes and volume changes occasioned by negative or positive displacement of fluid due to reciprocation of the piston rod and associated parts. This compensating device includes a collapsible and expansible container member, such as .a

, bellows having end plates or heads, providing an inclosed space which contains a vacuumor is substantially evacuated to tend to collapse the container member under pressure of the fluid in the chamber. Spring means is provided for urging the container to an expanded position and for balancing the container member in expanded positions against the collapsing force of the fluid in the chamber as such force varies in response to temperature olia ges and displacement of fluid. Preferably the cornpeiisating device is mounted within the aforesaid chamber. There is also provided in the hydraulic mechanism of the invention a construction and arrangement for sealthe piston rod where it passes through the housing {value provide a hermetic seal that retains the fluid the" housing with certainty and protects the sliding joint h u which t ist n r d. i ms T 16 stilling arrangement includes expansible and contractible nt ins, 1851 l ws, $1 r ui di the pis r d int y and" externally of the housing and being connected to the piston rod and the housing to provide a positive hermetic stat therebetwe en. The internal andyexternal bellows may he of generally. cylindrical configurationand may have, the same mean diameter. They are preferably spaced from the. piston rod to provide gas filled spaces are interconnected by passages providingfor flow of therebetween and for equalization of pressures within the bellows on each side of the housing wall.

Mo reover, in the double-acting, shock-resisting hydraulic mechanism of the invention, the piston is' of substantially the same length as its stroke and the openings of the side wall of the cylinder are disposed in a arter groups at the end portions of the side wall, one group'of openingsbeing closed by the piston at each end of its stroke whereby each group of openings controls reciprocation of the piston towards its end of the cylinder. To assist in this control, the end walls of the cylinder are provided with check valves that open inwardly of the cylinder to relieve vacuum as the piston mdves away from the end wall and close as the piston moves towards the end wall to allow the side openings to control rate of travel of the piston. The groups 'of openings may have different combined areas so that the forces required to move the piston on its instroke and outstroke difler and, thus, the rate of travel of the piston may be controlled. Adjustable tolerance compensating valves may be; provided in the cylinder end walls for establishing a regulable restricted communication be.- tween the cylinder and the chamber to regulate the final r'a'te of movement of the piston as it approaches an end irrespective of reasonable variations in the fit of the piston in the cylinder. i

Constructionsdesigned to carry out the invention will behereinafter described, together with other features of the invention.

"The invention will be more fully understood from a eading 'of the following detailed description and by reference to the accompanying drawings, wherein examplesfof the invention are shown, and wherein:

Fig. 1 is a longitudinal, sectional view of the hydraulic mechanism, constructed in accordance with the inventinn, showingits piston at the end of itsinstroke,

"Fig; 2.. is a transverse, sectional view, taken on the line 2--2 of Fig. 1,

Fig, 3 's a transverse, sectional 'view,'taken on the line of Fig. 1,

Fig. 4 is a view, similar to Fig. 1, showing the piston atthe endof its outstroke,

Fig. '5 is an enlarged, fragmentary, cross-sectional view'ofone of the adjustable valve'elements mounted in each end wall of the cylinder,

Fig. 6 is' a fragmentary perspective view, partly in sectionfshowing the rnoun ting'of one of-the check valves,

Fig. 7'is ai'view, similanto Fig. 1, 'of a modified hydrauic mechanism,'showing the piston immediately after cdmmeneementiofthe outstroke, I I

' o m a q i 4, ai hs m fisatiqnt showing the piston immediately after commencement of the instroke, and r Fig. 9 is a transverse, sectional view, taken on the line 9--9 of Fig. 8.

In Figs. 1 through 4 of the drawings, the numeral 10 designates the housing of a hydraulic mechanism or unit embodying the principles of the invention and of the double-acting, shock-resisting type which is particularly adapted for use in mounting railway car couplers in a draft gear as well as connecting parts of other equipment and machinery subjected to shocks. Although the hous ing 10 may be of any desired shape, preferably, it has a cylindrical bore or chamber 11 and an elongated side or peripheral wall 1 2. As will be explained, the chamber 11 is adapted to be completely filled'with a non-compressible fluid. A transverse wall 13 removably closes one end of the chamber, while its opposite end is closed by a em ab e ap Q: and Pl te b hi fa en to the ute 9 5 Qt th side l 2 b Suita e bolts T cap 14 has an axial opening 16 in which a bushing 17 is mg n sd p s l y su p ti h ut r end o ion of a piston rod or shaft 18. Mounting means, such as apertured lugs 19 and 20, are carried by the end wall 13, and the outer projecting end of the rod 18 for connecting the mechanism such as between a railway car or its center sill and one of its drawbars (not shown). Movement of the piston rod 18 with respect to the housing 10 may be confined within extreme limits by means of stops (not shown) in the mounting means, so that the, piston- 21, to be described, will stop short of engagement of the end walls of the cylinder on the in and out strokes.

The inner end of the piston rod is secured to a piston or plunger 21, as by a threaded joint (not shown), and the piston is reciprocablein a cylinder or working barrel 22 which is mounted coaxially inthe chamber 11' in spaced relation to the housing walls 12, 13 and 14. in addition to aside or peripheral wall 23, the cylinder 22 includes an enlarged outer end wall 24, form-ingfa "cylinder head and a cap or end plate 25, forming an opposite head attached to the inner end of the side wall by suitable bolts 26. An internal, radial flange 27 is provided in the chamber for receiving suitable bolts 28 to support the cylinder by its enlarged outer end wall 24, The flange 27 has a plurality of arcuate, elongated openings or slots 29,1externally of the end wall 24, to permit free cornmuni cation between the portions of the chamber 11 on opposite sides of said flange (Fig. 2). It is pointed out-that the Working barrel or cylinder is completely surrounded by the fluidin the chamber since its side and endwalls 23, 24 and 25 are spaced respectively'from the side and end walls 12, 14 and'13' of the housing. An axialopenin'gfit), having a bushing 31, is formed in the outer end wall 25 to slidably support the inner end portion of the piston rod 18'.

The cylinder 22 has a bore 32 in which the pis-tonfzl:

has a snug sliding fit and which communicates with'the chamber 11 through inner and outer groups or sets of apertures, openings or ports 33 and34 in the side Wall 23. If desired, one group of ports, such *as the ports 33 at the inner portion of the cylinder, may be larger and/or more numerous than the other group of ports 34' at the outer portion of said clinder. Thepiston 21 is,

of a length substantially equal to the length of its stroke andcoversone groupof portsat each end of said stroke (Figs. 1 and 4) whereby theinner ports 33'control the rate of travel of the 'instroke and the outer ports 3'4 control the rate of travel ofithe outstrokeofthe piston,

hen inner oup tr rt i r r. and/ ine, i pnemu hauth ste roup of ports... as own. the. instroke is faster and resistedless than the outstroke of the piston.

Arl t lit n sh eta v s emounted, a n

walls "Zflland ZS ofthe cyl'nderjto in antly relieye, the a wh ch; is ram: ehind t e. piston on main,

nam s ht' t aw f g t a d Walls an mtiaa aiuae Covering of theports. As shown most clearly in Fig. 6,.each check valve 35 includes a circular valve head or plate.36 disposed within .th'e cylinder 22 so. asto. overlie the inner ends of a pluralityof apertures 37 arranged in a circle in the end wall. An axialvalve stem 38,

having a nut 39 screw-threaded .on its outer end, is s ecured to each valve head 36 and extends through an, opening 40 in the cylinder end wall centrally ofthe ap'ertures 37 for slidably supporting the valve 35. Since the cylinder heads. Also, thecombined area of the side wall openings 33 and the check'va lve apertures 37 at the instroke end of the cylinder is sufliciently larger than the combined area of the side wall openings 34 so that the.

piston movement, on the outstroke, is controlled largely by the openings 34. Conversely, the combined. area of the apertures 37 in the outstroke end of the cylinder and the sidewall openings 34 issutficiently large that control of the piston movement on the instroke is largely under command of the sidewal-l'apertures 33.. Naturally, all of the openings and apertures exert some degree of control on piston movement and the disposition and relative sizes of the openings and apertures are so arranged'and constructed as to provide the desired rate .oflmovement of piston in either direction and .at any point. therein.

-In order to compensate for any variations in the fit of the piston in the cylinder and permit greater manufacturing variations than. conventional, an adjustable valve 41 is mounted in each of the end walls 24 and 25. As most clearly shown in Fig. 5, an opening 42 is formed in each cylinder end wall and has a counterbore 43 at its inner end with an outwardly-facing valve seat 44 therebetween. A metering pin or valve element 45 is screwthreaded in the outer end of the opening 42 and has a bevelled or tapered seating surface 46 at itsinnerend for coacting' with the seat 44. The metering pin 45 is held in adjusted positions by atlock nut 47 anda groove 48 extends longitudinally thereof to establish maximum constant communicationbetweenropposite sides of the end wall throughthe opening. Manifestly, theadjustable valves 41 can be set permanently, to provide preselected, uniform resistance to the reciprocation of the piston 21 into either of its extreme inner or outer posi-I tions irrespective of piston fit. The adjustableyalve .41

at the outstroke end of the cylinder can be closed off;

entirely if the leakage betweenthe bushing 31- and the piston rod '18 is s'uflicient to allow the piston to move slowly into the final position of Fig. 4. I

Inorder to eliminate the necessity of packing off between the piston rod 18 and the bushing 17 of the housing end wall 14, and to provide a hermetically sealed unit, expansible and contractible sealing means or bellows 49 and 50 surround the rod internallyand externally of the wall. The movable ends of the bellows 49 and 50 are secured to the rod by annular plates or collars 51 and 52, respectively, whileenlarged annular plates uated to a high degree from the industrial or-practical The pressure should be as low as possible, preferably less than oneinch of mercury absolute, and the lower the tothis. arrangement, a'positive hermetic seal isprovided between the piston rod and the end of the housing through which" said rod extendslfIhe. bushing 17 as 'well as the rod'portionwithin the'b'ellows are protected against fintemal as well as external; contamination andi leakage offluid from the chamber 11 is prevented. As

a result, the rod may have a relatively loose fitfin the. bushing ;-and may be permanently lubricated or allowed run dry. The fluid with the; mechanism need not necessarily be a good lubricant since it does nothave to lubricate the bushing 17. a

The outer sealing bellows 50 and inner sealing bel lows49 are vpreferably of substantially the same eifec-.

tive diameter and-may conveniently be of about the same lengthso that, on the instroke for example, as the outer. bellows contracts. in volume the inner bellows expands'in volume in about thesame amount. Both bellows are preferably filled with airor inert gas at about atmospheric pressure and the pressure within both the bellows is equalized through the intercommunicating openings 57. Moreover, when both sealing bellows have equal effective diameters and the rod diameter within the bellows is uniform, the presure of gas withinthe bellows remains the same for any stroke position of the In action, the pressure in either bellows piston rod 18. does not change significantly provided the intercommunicating openings 57 have a sufficiently large com bined area to take care of the required interchange of gas. from one bellows to the other. 7

Since the chamber 11 and cylinder 22 are adapted to be completely filled with a non-compressible fluid, it is very desirable to provide compensating means to accommodate variations of the volume of the fluid brought about by inward and outward reciprocation of the piston 21, its rod 18 and the internal sealing bellows 49. In accordance with the invention, the compensating means may be in the form of a pressure-responsive container member or bellows58 mounted in the chamber. A circular plate 59 is attached to one end of the bellows and is fastened to the housing end wall 13 by suitable bolts closure plate 63. Pairs of opposed pins 64 and 65 are,

carried by the plates 59 and 63, respectively, and have the ends of helical compression springs 66 confined thereupon for expanding the-bellows 58. The container or bellows construction provides an enclosed internal space that contains a vacuum; that is to say the space is evacpoint of view to provide therein a low absolute pressure.

pressure that can be achieved. the greaterthe advantage.

The container may be provided with a sealing composition 53 and 54-are carried by the fixed ends of the bellows v for connection to opposite sides offthe end wall by suitable screws 55 and 56. For'establishing communication between the interiors of the bellows, a plurality of openings 57 are formed in the end wall inwardly of thecentral peripheries-of the plates 53 and 54. As shown in Fig. 1, the external bellows 5t} collapses or contracts and the internal bellows 49 "elongates or expands upon inward reciprocation of the piston rod. When'the rod moves outwardly as shown'in Fig. 4, the internal bellows 49 contracts and the external bellows-50 expands. All of the joints between the housing end wall 14, the bellows and the piston rod are positively sealed. I Due atall joints to insure maintenance of the vacuum therein:

or it may be sealed as by welding or the like.

Whereas, the compression springs 66 in the compensating means may be constant displacement springs hav-. ing the characteristic of compressing in direct proportion;

to'the applied force, it is desirable to employ springs of the- 'non-linear displacement type exhibiting greater reduction in length under initial increments of load than under subsequent increments of load. With the latter type of; spring, the compensating unit will accommodate a given--decrease in effective volume of the internal chamber of the hydraulic mechanism with a lesser increase in internal pressure of the hydraulic fluid than where springs of the constant 'displ'acementtype are used.

In general, the volume of the compensating unit will be considerably greater than the volume change it is .de- I signed to accommodate so that the pressure within confined fluid will not change greatly from maximum to minimum volume.

Owing to the fact that the compensating unit contains a vacuum it is little afiected by changes in temperature,

andfluid pressures in the hydraulic unit in which it is'used are substantially independent of temperature changes ranges ordinarily encountered underfield conditions, the compensating unit acting to accommodate volume changes in the hydraulic fluid chamber without impus'iug' pres: sure variations engendered :by change in its own temperamm.

In the hydraulic mechanism of the invention, the pressure of the fluid in' the'cylinder. and chamber will ordinarily be approximately atmosphericpressure and this pressure will be maintained substantially'constant hy the compensating unit regardless of the. temperature or the position of the piston 21 and its rod '18. Pressures above or below atmospheric pressure may similarly be applied to and maintained in the hydraulic fluid.

Since'the hydraulic mechanism of the invention remains completely full of non-compressible'fiuid under all con ditions of operation it may be operated in any position such as horizontal, vertical or at an angle to the vertical.

As shown in Fig. l, the bellows 58' collapses or con tracts upon inward reciprocation of the piston 21 and its rod 18 and expands or elongates upon outward re-' ciprocation of said piston and rod (Fig. 4-). The effective volume of the chamber 11 is reduced by the elongationpf the internal sealing bellows 49 upon the instroke of the piston and rod. In view of the fact that the volume of the fluid remains substantially constant, the compensating means or bellows 53 is'highly advantageous to the operation of the hydraulic mechanism if the sealing bellows. is not to be distorted too much and the pressure of the hydraulic fluid is not to increase unduly. Due to the compensating means, which eliminates the need for breathing :by the mechanism, positive hermetic sealing of the mechanism is made possible. In addition, the compensating means accommodates variations in the volume of the fluid due to thermal expansion and contraction of the fluid and metallic parts of the mech-' anism. The compensating means may be located in a separate chamber apart from the housing but communi,

eating with the interior of the housing.

Due to its unique construction, the hydraulic mechanism is capable of use where shock resistance is desired or required. For example, the mechanism may be employed to absorb'or minimize the shock or impactof a falling weighted body, the stress applied in lifting heavy loads, the recoil of artillery and other sudden cessation of movement or change of direction encountered in various types of machinery and equipment; The mechanism is adapted to gradually absorb or easethe impact imposed on a' railway car or other equipment by applied force ih'ei-ther direction, such as when'a sudden blow or colli'sion occursor when a sudden pull or stress is exerted.

With reference to piston instroke, a sufficient number of openings 33' are provided in the side wall Z3of' the cylinder 22 to permit initial relatively rapid movement of the piston 21 at a spee'ddependent'upon the applied force. As the openings are closed by the instroke of the piston, the'combined flow area'is gradually restricted so as to gradually increase the resistance to'the inward reciprocation of the piston. As a result, the piston travels more slowly and its force is transmitted'to the cylinder and the housinglti so as to tend to'move saidhousing and-the'railway car or other object to which it is attached in the same direction, whereby the force applied to said piston through its rod 18 is cushioned so as'to minimize pistbn. The combined areasor the vaive'apenur'ess'r at the piston rod endv of the cylinder is suflicient to per-.

mit the tree flow of fluid from the chamber into the cylinder through the end wall. Therefore, the flow areas of the outer openings 34 have no great effect upon the rate of travelof the piston. V 7

Upon the outstroke of the piston; the outer ports 34 control its rate of travel which may be the same as or slower than the instroke. of the'inner cylinder wall 25 open immediately to relieve the vacuum behind the piston. Of course, the checkvalves at the opposite end of the cylinder are closed due to the piston movingtowa'rd the same. When the openlugs 34 are restricted, as shown, the outstr'oke of the piston is much slower than its instroke and its final outa ward movement is very slow since the outermost ports are closedjwhereb'y the only how is aroundthe piston and through the groove 43 of the adjustable valve 41.

The compensating-means or: bellows 58 is expanded by:

its springs 66 to compensate for the increased volume of the chamber and cylinder uponthe oustroke of the piston;

The arrangement of ports 33 and 34 to cause a relatively rapid instroke and a slower outstroke of the pistonis particularly suitable for railway draft gear because the mechanism as so constructed quickly absorbs and' dissipates upon instroke of the piston the sudden shocks encountered in coupling cars. Also, when a train is suddenly braked, the mechanism will readily absorb the forward impact of cars by instroke of thepiston. The-slower outstroke of the piston absorbs the more slowly applied stresses encountered in starting and accelerating a train; It will be apparent that the size and disposition of the ports 33 and 34 may be varied-to provide whatever piston' action is desired for the absorption of particular kinds and types of impact energies.

The construction of the compensating unit shown and described may be modified without departing from the invention. For example, the compensating unit 58 may be replaced by one or more Bellofram units, as manu= factured by the Bellowfram Corporation of Boston,

Massachusetts, and as modified in accordance with the present invention. The Bellofram unit includes a piston loosely fitted in a cylinder with a long stroke, flexible diaphragm extending across the cylinder and attached to the piston head. The piston is spring pressed in one direction; In accordance with the invention, the cylinder on'the spring sideof the piston is sealed and evacuated. The diaphragm at the other side is exposed 'to the hydraulic fluid in the fluidmechanism of the invention.

Another form of the invention is shown in Figs. 7, 8 and 9, and includes a housing similar to'the housing 1'0'and having a cylindrical bore or chamber 71 and an elongated sidewall 72. The housing may be square or angular in cross-section (Fig. 9). End walls 73 and 74 I are fastened to'the ends of the side wall 72 by suitable bolts 75 and 76, respectively, for closing the ends of the chamber 71. The end wall 74 has an' axial opening 77' through which a piston rod or shaft 78 slidably extends. Suitable mounting means, such as apertured lugs '79 and 30, are carried by the end wall 73 and'the outer projecting end of the rod 78 for connecting'the mechanism, for example, between the center sill'of a railway car and one of its drawbars. The piston rod has a piston 81 mounted thereon for reciprocation within a coextensive tubular sleeve 82 which is supported by the coaction of the side and end walls 72, 73 and 74 of the housing 70 in concentric, spaced relation to said wall.

A pair of transverse bulkheads or partitions'83 and between for the piston 81', with the partitions formingthe end walls of 'the' cylinder, Theportionrof' thesleeve 82; between the p rtit on s3 and s4- functious'as'" the Again, the check valves 35' ings or ports 86 therein for establishinggcommunication. between said cylinder and thechamber 71. Each'parti tion preferably has a'circurnferjential groove for receiving 7 an annular expansion member lorf split ring 88 which has its outer periphery confined in aj'co'mplementa'ry groove or recess 89 formed internally within the bore 'otYthe sleeve 82 (Fig. 9); A pair of diametrically-opposed;

openings 90 are formed in the sleeve in registration with' each groove 89 to permit accessto theexpansion rings. 88 for contraction thereof and removal of the partitions 83 and 84 when desired. Each partition includes two or more check valves 91, similarto the check valve 35, for relieving the yacuunr created behind the piston 81 upon reciprocation of said piston toward the other par-, tition.

the piston 81 and axial openings 93 and' 94are formed in the partitions to accommodate and slidably support the guide pin and the piston rod 78i Dueto the provision of the partitions, chambers 95 are formed in each end of the sleeve 82 between said partitions and the housing end walls 73 and 74 and these chambers communicate freely with the chamber 71 of the housing througharelatively large openings or ports 96, whereby said'chambers 1 are in effect one chamber. I

Expansible and contractible sealing means or bellows 97 and 98, similar to'the bellows '49and 50, surround the piston rod internally and externally of the housing end wall 73 so that it is unnecessary to pack off between said rod and the opening 77. It is believed unnecessary to described the bellows 97 and 98, but it is noted that the interiors of the same communicate through a plurality of openings 99 formed in the housing end wall.

Compensating means in the form of a pressure-responsive member or bellows 160, similar to the pressureresponsive member or bellows 58, is mounted on the end An axial guide pin or rod 92 extends inwardly from.

device exposed to the fluid in said chamber having a hermetically-sealed collapsible and expansible container member providing an enclosed space, 'saidspace being substantially evacuated to tend toicollapse said container member uiider pressure ofithe fluid in said chamber, and spring means balancing said chamber member in expand'ed positions against the collapsing force of the fluid insaid' chamber as said force varies in response to temperature changes and displacement of said fluid due to reciprocation of saidpiston rod.

2. A hydraulic mechanism as defined in claim l wherein said compensating device is mounted said chamber amd said spring means'is mounted within said container member. t n

3. .A hydraulic mechanism, as defined in claim 1' wherein saidcornpensating device is mounted within said chamber"and said spring means comprises a compression spring/mounted within saidcontainer member of nonlinear "reaction exhibiting greater reduction inlength under initial increments of load than under subsequent increments" of load.

4. Ajshoclc-resisting hydraulic mechanism including a hermetically-sealed housing, a cylinder having end and sidewalls mounted in said housing and providing a chamber' between said cylinder and said housing, at least one i of the end walls of said cylinder being spaced from the walls of said housing, a wall of said cylinder having open- 'ings establishing communication between said cylinder and said chamber, a piston reciprocable in saidcylinder between its end walls, a piston rod connected to the piston and reciprocably extending to the exterior through said wall 74 so as to be exposed to the non-compressiblefluid V guide pin92- similarly to the mechanism of Figs. 1 to 6 hereinbefor'e described, its method of operation will be apparent; 'It will be seen that, in accordance with the invention, fluid pressures within the working cylindelr'may build up to considerable magnitudes during moments when the piston is reciprocating and the mechanism is absorbing energy. However, even duringthese moments, pressures within the communicating chamber outside of the cylinder do not increase very much due to the throttling efiect of the openings in the side wall of the cylinder and the pressure ofisetting eiiect of the compensating unit.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention. I claim: I n

g 1. A shock-resisting hydraulic mechanism comprising a housing, a cylinder having end andside walls mounted V in said housing and providing a chamber between said cylinder and said housing, a wall of "said cylinder having openings establishing communication between said cylinder and said chamber, apiston reciprocable in -said cylinderbetween its end walls a piston rod connected to the piston and reciprocably extending to'the exter'ior through one of the end walls of'said cylinder and sealingly through said housing, said'chamber and cylinder being completely filled with a non-compressible fluid,

one end wall ofsaid cylinder and through a wall of said housing, expansible and contractible sealing sleeves surf rounding the piston rod internally and externally of said housing, and connecting said piston rodto the-wall of said housing to provide a positive-hermetic seal therebetween, and passage means providing communication between the spaces within said 1 internal and external sealing sleeves for equalizing pressures within said sleeves, said internal sealing sleeve being disposed in said chamber between said cylinder and said housing.

I 5. A hydraulic mechanism'as defined in claim 4 wherein said sealingsleeves comprise internal and external bellows elements connected between said piston rod and the inner and outer surfaces of-the wall of said housing.

,6. A hydraulic mechanism as defined in claim 4 wherein said sealing sleeves comprise internal and external bel lowselements of generally cylindrical configuration :and having the same mean diameter connected between said pistonrodand the inner and outer surfaces of the wall of said housing. i i

7. A hydraulic mechanism as defined in claim 4 wherein said sealing sleeves comprise internal and external bellows elementsconnected between said piston rod and the inner and outer surfaces of the Wallof said housing, the undulating walls of said bellows elements being spaced from said piston rod to providelgas filled spaces between said bellows elements and .theportion of said piston rod surrounded thereby. 7

anism comprising ,a hermetically-sealed housing, a cylinder mounted infthe housing and having end and side walls spaced from the walls of said housing to provide with said housing a continuous chamber surrounding the endandside walls of the cylinder, the'side wall of said cylinder having openings establishing communication between, the chamber and cylinder, a piston reciprocable in said cylinder between its end walls, a piston rod'connected to the piston andreciprocably extending to the posed in a pair of groups at the end portions of said side I wall, one group of openings being closed by said piston 8. A doubleaacting, shock-resisting hydraulic mechat each end of its stroke, and large, inwardly-opening, check valve means,'one in eachend'wall of said cylinder,

eacli'said check; valve means, when open establishing cornmunicationbetween said chamber and said cylinder,

whereby each-group of openings controls reciprocation of said piston towards its end of the cylinder.

- 9.-A double-acting; shock-resisting hydraulic mech anism comprising a hermetically sealed housing, a cyl indei' mounted in the housing and having end and side' walls spaced from the walls of'said' housing to provide a' ings being closed by, said piston at each end of' its stroke,

said chamber and said cylinder being completely filled with a non-compressible fluid, expansible and contractible sealing bellows surrounding the piston rod internally and externally of said casing and connecting said 'piston rod to the wall of'said housing to provide a positive hermetic seal therebetween, passage means providing communicati on between the spaces said bellows for equalizing pressures within said" bellows, inwardly opening check valves in -the end walls of said cylinder, and a substantially temperature insensitive compensating device mounted in'said" chamber and having a hermeticallysealed collapsible and expansible container member exposed to the fli id in said chamber, said container providing'an enclosed space substantially evacuated to tend to collapse said container under pressure of the fluid in said'chamber, and spring means balancing said container member; in expanded positions against the collapsing force of the-fluid in said chamber as said force varies in response totemperature changes and displacement of said fluid due to expansion and contraction of the inner 12 being substantially evacuated to tend to collapse said container member under pressureof said fluid, and resilientme'ans balancing said container member in expanded positions against the collapsing force of said limits and said sealing means fluidas said force varies in response to temperature changes and'dis placement of said fluid due to reciprocation of" said rod, whereby in operation of said mechaexpansible and contractible sealing sleeve surrounding the rod internally of said housing and connecting'said rod to the Wall of said housing to provide a positive hermetic seal therebetween; vent means communicating the interior of said sealing sleeve with the exterior of said housing; said housing providing a chamber enclosing said internal sealing sleeve, saidinternal sealing sleeve upon reciprocation varying the volume of said chamber; a body of non compressible fluid in and completely filling said chamber;

- and a substantially temperature insensitive compensating reciprocation of said internal sealing sleeve, whereby in of said sealing-bellows as said piston rod is reciprocated.

10. A hydraulic mechanism comprising: a housing; an opeuatingrod' extending through a wall and beingrecipro'cable through'said Wall; means reciprocably' sealing said rod in said Well; said housing providing a chamber enclosing a portion of said' rod, said rod upon reciprocation varying the volume of'said chamber;

a body'of' non-compressible fluid in and completely fill-' ing-said chamber; and a substantially temperature insensitive compensating, device exposed to the" fluid in said chamber, said compensating device including a hermetica'lly-sealed, collapsibleand expansible container member providing an enclosed space, said space being substantially evacuated'to tendto collapsesaid container member under pressure of said fluid, and resilient means balancing said contaiiier'member in expanded positions against the collapsing force of'said fluidas'said force varies in' re sponse to temperature changes and displacement ofsa id providing a chamber enclosing a portion of said rod;

said rod upon reciprocation-varying the volume of said chamber; a body'of non-compressible fluid in and cornpletely fillingsaid chamber; and a substantially temperature insensitivecompensatiang device'imniersedin the I y sealed, collapsible and 'expansible contaiii'ermerrrber 'providingan enclosed space, saidspac'e' of said housing"- device exposed to the fluid in said chamber, said compensating device including a'hermetically-seale'd, collapsible and expansible container member providing an enclosed space, said space being substantially evacuated to ;tend to collapse said container member under pressure of said fluid, and resilient means balancing said chamber member in expanded positions against the collapsing force of said fluid as said force varies in response to tern perature changes and displacement of said fluid due to operation of said mechanism the pressure of said fluid remains within narrow limits 'and said internal sealing sleeve is subject to no undue pressure variations.

l3. A hydraulic mechanism comprising: a housing; an operating rod extending through a Wall of said housingand being reciprocable through said Wall; means reciprooably sealing said rod in said 'wall including expansible and contractible sealing sleeves surrounding the rod internally and externally of said housing and connecting said rod to the Wall of said housing to'provide a positive hermetic seal therebetween, and passage means providing communication between the spaces within said, in-

ternal and external sealing sleeves for equalizing'pressures within said sleeves; said housing providing a chamber enclosingsaid iternal sealing sleeve; said internal sealing sleeve upon reciprocation varying the volume of said chamber; a body of non-compressible fluid in and completely filling said chamber; and a substantially temperature insensitive compensating device immersed in the fluid in said chamber, saidcompensating device including a hermetically-scaled, collapsible and expansible container member providingan enclosed space, said space being substantially evacuated to tend to collapse said container member under pressure of said fluid, and resilient means balancing said chamber member in .ex-t panded positions against the collapsing force of saidfluid' as said force varies in response to temperature changes and displacement of said fluid due to reciprocation-of said internal sealing sleeve; whereby in operation of 'said mechanism the pressure of said fluid'remains within narrow limits and said internal sealing sleeve is subject to no undue pressure variations.

.14. A'doublc t-acting; :shodk-resisting hydraulic rnechanism for railway-car couplings including a hermeticallysealed housing having end and side walls, a cylinder mounted in the housing and having end and side Walls spaced from theiwa'lls; of said housing to provide a chamber surrounding the cylinder, the side walls ofsai'd cylinder having openings establishing communication between li e ibranq; lind r 1 P n esi rQa f a said cylinder between its end walls, a piston rod con- 13 treated to the piston and extending to the exterior through one of the end walls of said cylinder and housing, expansible and contractible sealing means surrounding the piston rod internally and externally of the chamber and connecting said rod to the end wall of the housing to provide a positive hermetic seal therebetween, said chamber and cylinder being completely filled with a non-compressible fluid, and spring pressed compensating means containing a vacuum mounted in said chamber to accommodate thermal expansion and contraction of the noncompressible fluid and variations in the volume of said chamber due to the displacement of the piston rod.

15. A double-acting, shock-resisting hydraulic mechanism for railway car couplings including a hermeticallysealed housing having end and side walls, a cylinder mounted in the housing and having end and side walls spaced from the walls of said housing to provide a chamber surrounding the cylinder, the side walls of said cylinder having openings establishing communication between the chamber and cylinder, a piston reciprocal -in said cylinder between its end walls, a piston rod connected to the piston and extending to the exterior through one of the end walls of said cylinder and housing, expansible and contractible sealing means surrounding the piston rod internally and externally of the chamber and connecting said rod to the end wall of the housing to provide a positive hermetic seal therebetween, said sealing means including internal and external bellows carried by the piston rod and connected to the inner and outer surfaces ofthe end wall of the housing, said chamber and cylinder being completely filled witha noncompressible fluid, .and spring-pressed compensating means containing a vacuum mounted in saidcham'ber to accommodate thermal expansion and contraction of the non-compressible fluid and variations in the volume of said chamber due to the displacement of the piston rod.

16. A double-acting, shock-resisting hydraulic mechanism for railway car couplings including a hermeticallysealed housing having end and side walls, a cylinder mounted in the housing and having end and side walls spaced from the walls of said housing to provide a chamber surrounding the cylinder, the side walls of said cylinder having openings establishing communication between the chamber and cylinder, a piston reciprocal in said cylinder between its end walls, a piston rod connected to the piston and extending to the exterior through one of the end walls of said cylinder and housing, and expansible and contractible sealing means surrounding the piston rod internally and externally of the chamber and connecting said rod to the end wall of the housing to provide a positive hermetic seal therebetween, said sealingmeans including internal andv external bellows carried by the piston rod and connected to the inner and outer surfaces of the end wall of the housing.

'17. A double-acting, shock resisting hydraulic mechanism comprising a hermetically-sealed housing, a cylinder mounted in said housing and spaced fromthe inner walls thereof to provide with said housing a continuous chamber surrounding the end and side walls of the cylinder, said cylinder having openings establishing communication between said chamber and said cylinder, a piston reciprocable in said cylinder, a piston rod connected to said piston and reciprocably extending to the exterior through one of the walls of said cylinder and sealingly through said housing, the openings of said cylinder being disposed in a pair of groups at opposite ends of said cylinder, and large, inwardly-opening, check valve means, one in each end of said cylinder, each said check valve means when open establishing communication between said chamber and said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 404,012 Nickerson May 28, 1889 1,072,350 Muller Sept. 2, 1913 1,109,996 Kuhlmann Sept. 8, 1914 1,220,972 Fulton Mar. 27, 1917' 2,096,094 Dube et al. Oct. 19, 1937 2,314,404 Katcher Mar. 23, 1943' 2,333,096 Dowty .4 Nov. 2, 1943 2,431,200 Rosenberger Nov. 18, 1947 2,770,003 Comey et -al. Nov. 13, 1956 2,778,259 Moir Jan. 22, 1957 2,866,223 Van Dillen Dec. 30, 1958 FOREIGN PATENTS 154,419 Austria Sept 26, 1938 986,649 France Apr. 4, 1951 1,057,048 France Oct. 28, 1953 

